Evidence fromαDecay ThatZ=82Is Not Magic for Light Pb Isotopes

To resolve the reported anomalous behavior of the $\alpha$-decay rates of ${}_{}{}^{186,188,190,192}{}_{}{}^{}\mathrm{Pb}$ we determined more accurate $\alpha$-decay branches for these isotopes. Our data result in $\alpha$-decay reduced widths whose dependence on $N$ is similar to that observed for other elements. However, contrary to the expectation of a shell effect at $Z=82\mathrm{}$, this new information indicates lead nuclei to be less hindered toward $\alpha$ decay than mercury isotopes. It appears that midway between $N=82\mathrm{}$ and $N=126\mathrm{}$ the proton number of 82 is not magic.